Hi @Notori - in essence - the idea would work - however there may well be a better way - you can get string-sets for 5-string violins ( well, usually you have to buy the C separately ).   I did something very similar on an old 4/4 (acoustic) fiddle - just moved the G, D, A "up a notch" on the pegs and got a C string (not a viola C - I did TRY that,  specifically it was a Zyex VIOLA C - but it was far too "sloppy" and needed a lot of attention to play it well) - so I junked it and I ended up getting a Thomastik Vision VIOLIN C - and voila! a 4/4 fiddle working as a viola.    OK - it doesn't have the richness and timbre of a real viola - but it's in range and perfectly playable - which - for the moment - is all that matters !

Hope that helped !